Postcontrast computed tomography in subarachnoid hemorrhage from ruptured aneurysms.

Computed tomography (CT) scans of 49 patients with subarachnoid hemorrhage (SAH) secondary to ruptured aneurysms were reviewed. Subarachnoid blood was detected in 95% when CT was performed within 5 days after the bleeding. Prediction of the site of the ruptured aneurysm from distribution of the cisternal blood varied from 92% for the anterior cerebral artery aneurysms to 70% for the middle cerebral and 47% for the internal carotid artery aneurysms. Following plain CT scans, postcontrast studies were performed in 27 patients. Aneurysms were directly visualized in 8 cases and subarachnoid enhancement was noted in 21. In 3 cases, subarachnoid enhancement made possible a correct diagnosis of SAH in the absence of evidence of cisternal blood on precontrast CT scans.